What's Causing Cancer?
In the war against cancer, incidence and mortality rates of some cancers continue to increase, and scientists continue to search for answers about causation. Integral to this debate is the question of what role environmental factors play in the cancer crisis. In the first Focus article, experts on both sides comment on the current state of the knowledge and the possible impact of pesticides, air pollution, environmental tobacco smoke, metals, and radioactivity on the development of cancer.
Sorting out Recycling
Every day Americans dutifully sort their trash and fill their separate bins with glass, plastic, paper, and other reusable wastes, with the assumption that recycling is economically sound and environmentally friendly. Although advocates point to the decreased need for landfills and the conservation of forests as evidence of recycling's benefits, critics emphasize that recyling sometimes requires more energy, and is less economical, than using virigin materials. The second Focus article takes a critical look at the advantages and disadvantages of recyling to assess its true value.
Better Toxicity Tests
The quest for alternatives to animal testing continues. Recently developed skin and eye analogs, discussed in Innovations, allow a variety of soluble and nonsoluble materials to be tested without using animals. An added benefit is that these in vitro systems provide information about mechanisms of action of toxic responses. These systems take on additional importance as 1998 approaches, the year the European Commission expects all cosmetics companies to test their products using in vitro methods when possible.
Childhood Cancer and Radiation
Wakeford reviews the risk of childhood cancer from exposure of pregnant women to ionizing radiation and reports that epidemiologists now contend that intrauterine irradiation and childhood leukemia are causally related, although the same relationship with respect to solid tumors remains questionable. However, he contends there is no association between childhood leukemia and paternal preconceptional irradiation and states that a causal interpretation of this association has been abandoned by scientific experts.
Toxicity of Second-Hand Smoke
Bascom et al. show that acute exposure to sidestream tobacco smoke is capable of altering clearance of foreign material inhaled through the nose, reducing the normal clearance rate of nasal mucous. However, there was a high degree of variability among human subjects exposed to cigarette smoke for one hour in inhalation chambers, resulting in 6/12 subjects exhibiting a faster rate of clearance, 3/12 showing no change after exposure, and 3/12 displaying substantial decreases in clearing rates. In two subjects the toxic effects persisted for two hours after smoke exposure. More studies are needed to explain the basis for the extreme biologic variability and to advance knowledge of the pathogenesis of the chronic effects of environmental tobacco smoke.
Iodine in the Space Capsule
Astronauts experiencing extended space travel will use iodine to disinfect their drinking water. There is potential for iodine toxicity, and the levels must be monitored to ensure safety as well as efficacy of the disinfectant. Zareba et al. examined the utility of hair, saliva, and urine as sources for biological monitors of iodine exposure. They found that hair was unsuitable as a medium for monitoring, saliva was a good possibility because it can be collected noninvasively, but urine levels of iodine adjusted to creatinine were the most useful media for biological monitoring of iodine in astronauts.
Lead in Mexican Children
Children living in Mexico City exhibit blood lead levels ranging up to 31 micrograms/dl, with 44% exceeding 10 micrograms/dl, levels known to cause developmental neurotoxicity. Romieu et al. looked at 200 children younger than 5 years old and determined that lead-contaminated pottery and lead in dirt from children's hands, along with the use of leaded gasoline, were the major sources of lead exposure. The authors recommend education and information programs to reduce the use of lead-contaminated cookware and to reinforce the use of unleaded gasoline.
Accurate Radon Measurements
Weinberg reports that particulate indoor air pollution can affect the accuracy of radon measurements. The amount of radon that has accrued can be measured by examining decay products deposited on glass objects that were continually present in occupant's homes. Uncertainties that arise about such measurements can distort inferences from epidemiological studies, such as the risk of lung cancer from radon exposure or potential synergism between radon exposure and cigarette smoking. More methodological work is needed, but in the meantime, houses with excessive risk of radon exposure could be identified and remediation started.
Chelation for Toxic Metals
A Commentary by Goyer on chelation therapies for toxic metals reminds us that there there is an incomplete understanding of chelation therapy, and its effectiveness is unproven. In a related Meeting Report, Goyer et al. summarize the results from a conference held at the NIEHS on the role of chelating agents for the prevention, intervention, and treatment of exposures to toxic metals. Lead chelation using EDTA, succimer, and d-penicillamine are discussed, as are topics covering chelation therapy for mercury, cadmium, copper, and the radioactive actinide elements. Some of the research recommendations include determination of optimal routes of administration for chelating agents, potential advantages for the simultaneous administration of multiple chelating agents, and designs for novel methodological and experimental approaches to studying the potential side effects associated with chelation.
Last update: November 20, 1995 |
